More than 5,000 Iraqi army and paramilitary troops backed by U.S. soldiers swept into this insurgent stronghold near the Syrian border Saturday, conducting house-to-house searches and battering down stone walls in the narrow, winding streets of the old city.

Late Saturday, the prime minister ordered the Rabiyah (search) border crossing closed in an attempt to stanch the flow of insurgents from Syria, which is about 60 miles from Tal Afar.

While several hundred insurgents using small arms initially put up stiff resistance in the city's ancient Sarai district, Iraqi forces reported only two men wounded in the day's fighting. The U.S. military issued no casualty report for the 3,500 Americans in the operation.

Interior Minister Bayan Jabr (search) said 48 insurgents had been captured.

As the day wore on, fighting quickly died down, said Col. H.R. McMasters (search), commander of the 3rd Armored Cavalry Regiment. He said the joint force found the Sarai neighborhood nearly deserted once the shooting ended.

"The enemy decided to bail out," he said, adding that 150 insurgents had been killed the last two days. Jabr put the number at 141 and said five government soldiers died and three were wounded in the same period.

McMasters said the vast majority of insurgents captured in that period were "Iraqis and not foreigners." Iraqi officials said Thursday that they had captured 150 foreign fighters.

South of Baghdad, police made the gruesome discovery of 18 men who had been handcuffed and shot to death after being abducted two days ago from their Shiite Muslim neighborhood in Iskandariyah, 30 miles south of the capital.

In recent weeks, dozens of bodies have been recovered, the apparent victims of tit-for-tat vengeance killings by Shiite and Sunni Arab death squads.

Baghdad International Airport reopened Saturday after a 24-hour closure, begun when a British security firm stopped working because it had not been paid for seven months. After overnight negotiations, the government agreed to pay half of what it owed, and employees of the London-based Global Strategies Group were ordered back to work.

With the Tal Afar offensive under way, the Iraqi defense minister signaled his U.S.-trained forces would not stop after this operation and vowed to move against insurgent bastions throughout the country.

"We say to our people ... we are coming," said Defense Minister Sadoun al-Dulaimi.

The latest drive against the stubborn insurgency began with just over a month to go until Iraqis vote on adopting a permanent constitution

Wrangling during the drafting of the charter, which faces stiff opposition from the country's Sunni Arab minority, highlighted distrust among Iraq's volatile ethnic and religious mix as well as worries that Iraq might eventually split apart.

Sunnis claim the document favors the long-oppressed Shiite majority and the Kurds, who have run a semiautonomous state in the north since the end of the first Gulf War. Both Shiites and Kurds appear eager to set up a loose confederation of mini-states after decades of repression by a centralized government in Baghdad.

The offensive in Tal Afar, 260 miles northwest of Baghdad, is especially delicate because of the tangle of ethnic sensitivities.

About 90 percent of the city's 200,000 people — most fled to the countryside before the fighting — are Sunni Turkmen who have complained about their treatment from the Shiite-dominated government and police force put in place after the U.S. invasion in 2003.

Addressing that complaint, Jabr announced Saturday that 1,000 additional police officers would be hired in Tal Afar after the offensive and that they would be chosen from the Turkmen population.

The Turkmen have a vocal ally in their Turkish brethren to the north, where Turkey's government is a vital U.S. ally and has fought against its own Kurdish insurgency for decades. Tal Afar is next to land controlled by Iraqi Kurds.

Turkey voiced disapproval of U.S. tactics when American forces ran insurgents out of Tal Afar a year ago. The Turkmen residents complained that Iraqi Kurds were fighting alongside the Americans.

U.S. and Kurdish officials denied the allegation, but the Turkish government threatened to stop cooperating with the Americans. The siege was lifted the next day and insurgents began returning when the Americans quickly pulled out, leaving behind only a skeleton force of 500 soldiers.

For those reasons, U.S. forces stood back during the new sweep through Tal Afar, allowing Iraqi forces to break down doors in the search for insurgents. The Americans followed behind, securing positions while the Iraqis advanced.

"I can see why the terrorists chose this place for a fight, it's like a big funnel of death," Sgt. William Haslett of Rocklin, Calif., said of the twisting streets and alleys Tal Afar's old city.

Twelve hours after the offensive began, Prime Minister Ibrahim al-Jaafari said insurgents had been trying to "to isolate Tal Afar from the political process as we are preparing for the referendum on the draft constitution."

Al-Dulaimi, who joined al-Jaafari at the news conference, said he expected the offensive to last three days and complained Iraq's neighbors had not done enough to stop the flow of foreign fighters.

"I regret to say that instead of sending medicines to us, our Arab brothers are sending terrorists," al-Dulaimi said.

The interior minister read al-Jaafari's order closing the border on Iraqi television late Saturday.

The decree indefinitely shut the Rabiyah crossing to all transportation, including the railroad, except for vehicles with special permission from the Interior Ministry.

The order did not affect the frontier crossing near the insurgent stronghold of Qaim or the major highway into Syria.

In other developments Saturday:

—Jordan's Prime Minister Adnan Badran visited Baghdad, meeting with Iraqi Vice President Adel Abdul Mehdi in a symbolic show of support that was seen as an attempt to shore up relations between the Arab neighbors.

—Iraqi police seized a huge cache of explosives hidden in a gravel truck heading for the holy city of Karbala, where tens of thousands of Shiite Muslims were to begin assembling to celebrate the birth of Imam al-Mahdi — one of Shiite Islam's most important holidays.